Hurricane Wilma's march toward Florida slowed Thursday, giving residents an unexpected extra day to prepare for the storm, while authorities stockpiled emergency supplies.

Forecasters at the National Hurricane Center said Wilma will likely strike Florida's western coast late Sunday, more than a day later than previously thought.

Max Mayfield, the center's director, said the slowdown will likely weaken the storm from a Category 4, with sustained 150 mph winds, to a Category 3 or less before it makes landfall in the United States.

"The timing is certainly working in our favor," Mayfield said. But he added that Wilma probably will still be a strong hurricane with a powerful storm surge when it reaches the state. Category 3 storms have winds of 111 mph to 130 mph.

Gov. Jeb Bush (R) declared a state of emergency to ensure that necessary supplies and disaster response teams are in place. "This is the time to prepare," Bush said.

The storm was predicted to make a turn to the northeast toward Florida after striking Mexico's Yucatan Peninsula in the western Caribbean.

Mayfield said Wilma is unusually large, with tropical storm-force winds extending about 260 miles from the center that could cause widespread damage.

At 11 p.m. Eastern time, forecasters said Wilma was about 100 miles southeast of Cozumel, Mexico, and about 455 miles southwest of Key West. It was heading northwest at 6 mph toward Mexico's Yucatan Peninsula, where Mayfield said it could do catastrophic damage.

The storm had strengthened slightly, and forecasters said it could regain Category 5-strength winds of 156 mph or more.

Although Wilma was expected to approach from the west, forecasters warned that major Atlantic Coast cities including Miami, Fort Lauderdale and West Palm Beach could be hit by strong winds and heavy rains.

Bush said the state had food, water, ice and other supplies ready, as well as disaster-response teams that include as many as 7,500 National Guard troops. "We are battle-tested, well-resourced, well-trained," he said.

The Federal Emergency Management Agency was positioning emergency materials in Jacksonville, Lakeland and Homestead. FEMA acting chief R. David Paulison said that the agency has 150 truckloads of ice and 150 truckloads of water, and that the American Red Cross has 200,000 meals available.

"We are ready for the storm, as much as you can be," Paulison said in Washington.

In the low-lying, vulnerable Keys, the normally crowded historic district in Key West was eerily quiet. Tourists and nonresidents had already been asked to leave. A mandatory evacuation of residents was expected to start Friday, although some did not seem to be hurrying.

Hurricane Wilma hit Puerto Castilla, Honduras, and weakened slightly as it roared toward Mexico's Yucatan Peninsula and South Florida.